A 24-year-old patient presents with urethral discharge. Thayer-Martin medium yields smooth gray translucent colonies after 3 days; Gram stain shows Gram-negative diplococci in kidney-bean shape. Which organism is suspected?

Prepare for the CAMLPR Microbiology Test. Utilize flashcards and engaging multiple-choice questions, each equipped with descriptions and explanations. Ready yourself for an excellent performance!

This presentation points to gonococcal urethritis caused by Neisseria gonorrhoeae. Thayer-Martin medium is a selective culture medium designed to isolate Neisseria species from clinical specimens by suppressing competing flora with antibiotics. Growth on this medium as smooth, gray, translucent colonies after a couple of days fits N. gonorrhoeae. The Gram stain showing Gram-negative diplococci in a kidney-bean arrangement is a classic clue for Neisseria species, and in the context of urethral discharge strongly supports N. gonorrhoeae rather than other organisms.

Neisseria meningitidis can look similar on a stain, but it is typically associated with meningitis or septicemia, not urethral discharge. Moraxella catarrhalis is a respiratory tract inhabitant and has different clinical relevance and colony behavior, while Haemophilus ducreyi causes chancroid with ulcers and requires different growth factors, not the selective Neisseria medium described.